Lua Add Emergency Garbage Collector

Derivative of work by RobertGabrielJakabosky
 http://lua-users.org/wiki/EmergencyGarbageCollector

I've only implemented the not enough memory part and
 expanded this idea to adding a mechanism to signal
 the OOM condition of the plugin buffer which allows us to only
 grab the playback buffer after garbage collection fails
 (SO THE MUSIC KEEPS PLAYING AS LONG AS POSSIBLE)

Change-Id: I684fb98b540ffc01f7ba324ab5b761ceb59b9f9b

1 files changed, 16 insertions, 6 deletions

diff --git a/apps/plugins/lua/lapi.c b/apps/plugins/lua/lapi.c
index 487d6b173a..6426cd94a9 100644
--- a/apps/plugins/lua/lapi.c
+++ b/apps/plugins/lua/lapi.c
@@ -547,7 +547,9 @@ LUA_API void lua_getfield (lua_State *L, int idx, const char *k) {
   lua_lock(L);
   t = index2adr(L, idx);
   api_checkvalidindex(L, t);
+  fixedstack(L);
   setsvalue(L, &key, luaS_new(L, k));
+  unfixedstack(L);
   luaV_gettable(L, t, &key, L->top);
   api_incr_top(L);
   lua_unlock(L);
@@ -656,14 +658,14 @@ LUA_API void lua_settable (lua_State *L, int idx) {
 
 LUA_API void lua_setfield (lua_State *L, int idx, const char *k) {
   StkId t;
-  TValue key;
   lua_lock(L);
   api_checknelems(L, 1);
   t = index2adr(L, idx);
   api_checkvalidindex(L, t);
-  setsvalue(L, &key, luaS_new(L, k));
-  luaV_settable(L, t, &key, L->top - 1);
-  L->top--;  /* pop value */
+  setsvalue2s(L, L->top, luaS_new(L, k));
+  api_incr_top(L);
+  luaV_settable(L, t, L->top - 1, L->top - 2);
+  L->top -= 2;  /* pop key and value */
   lua_unlock(L);
 }
 
@@ -674,7 +676,9 @@ LUA_API void lua_rawset (lua_State *L, int idx) {
   api_checknelems(L, 2);
   t = index2adr(L, idx);
   api_check(L, ttistable(t));
+  fixedstack(L);
   setobj2t(L, luaH_set(L, hvalue(t), L->top-2), L->top-1);
+  unfixedstack(L);
   luaC_barriert(L, hvalue(t), L->top-1);
   L->top -= 2;
   lua_unlock(L);
@@ -687,7 +691,9 @@ LUA_API void lua_rawseti (lua_State *L, int idx, int n) {
   api_checknelems(L, 1);
   o = index2adr(L, idx);
   api_check(L, ttistable(o));
+  fixedstack(L);
   setobj2t(L, luaH_setnum(L, hvalue(o), n), L->top-1);
+  unfixedstack(L);
   luaC_barriert(L, hvalue(o), L->top-1);
   L->top--;
   lua_unlock(L);
@@ -903,11 +909,11 @@ LUA_API int lua_gc (lua_State *L, int what, int data) {
   g = G(L);
   switch (what) {
     case LUA_GCSTOP: {
-      g->GCthreshold = MAX_LUMEM;
+      set_block_gc(L);
       break;
     }
     case LUA_GCRESTART: {
-      g->GCthreshold = g->totalbytes;
+      unset_block_gc(L);
       break;
     }
     case LUA_GCCOLLECT: {
@@ -924,6 +930,10 @@ LUA_API int lua_gc (lua_State *L, int what, int data) {
       break;
     }
     case LUA_GCSTEP: {
+      if(is_block_gc(L)) {
+        res = 1; /* gc is block so we need to pretend that the collection cycle finished. */
+        break;
+      }
       lu_mem a = (cast(lu_mem, data) << 10);
       if (a <= g->totalbytes)
         g->GCthreshold = g->totalbytes - a;